This invention relates to video driver circuits and more particularly to voltage-to-current converters for receiving input voltage signals related to a video input signal and control of the video output signal by analog input, contrast, and brightness signals.
Wide bandwidth amplifiers are used to amplify video signals. Such wide-band amplifiers are described, for example, in "A New Wide-Band Amplifier Technique", Barrie Gilbert, IEEE Journal of Solid-State Circuits, Vol. SC-3, pages 353-365, December 1968; "Design Techniques for Monolithic Operational Amplifiers", Robert J. Widlar, IEEE Journal of Solid-State Circuits, Vol. SC-4, No. 4, pages 184-191, August 1969; "Amplifying Devices and Low-Pass Amplifier Design", John Wiley & Sons, 1968; and U.S. Pat. No. 3,849,735.
Of importance, wide bandwidth amplifiers typically require response down to DC, thereby precluding AC coupling. Video standards used throughout the world require video signals to be referenced to ground, thereby requiring the use of wide bandwidth, single ended amplifiers. Unfortunately, the prior art has not provided a wideband, single ended, DC coupled monolithic amplifier suitable for use, for example, with video signals.
Gilbert, particularly with respect to FIG. 8 and the discussion pertaining thereto, describes a circuit fabricated with bipolar transistors which is used for providing an output current which is the product and quotient of three separate input currents. Widlar describes a variety of techniques for use in designing operational amplifiers. U.S. Pat. No. 3,849,735 describes a wide-band differential amplifier for converting the difference between two input currents to a voltage. U.S. Pat. Nos. 3,430,155 and 4,061,959 describe techniques for biasing bipolar transistors. "Analysis and Design of Analog Integrated Circuits" (Gray and Meyer, John Wiley & Sons, second edition, 1984) describe the use of feedback in analog amplifiers.